The invention relates to a gas turbine combustion chamber of the type having a double-walled annular flame tube.
Air supply bushings are required in combustion chambers of this type, for example, fully or partially to fulfill the combustion mixing or cooling air requirements for the various reaction zones in the combustion chamber.
The air supply bushings must be so arranged that, despite the double-walled nature of the flame tube structure, an air throughput, unimpeded as regards volume and speed, is permitted from the external secondary air channel, between the flame tube and the combustion chamber outer housing, into the various reaction zones.
In combustion chambers of the type recited hereinabove, known from German Published Unexamined Patent Applications OS 19 33 821 and OS 29 13 223, the air supply bushings are permanently integrated into the flame tube structure and welded, for example, to the flame tube structure or, as additionally mentioned and shown in the case of German OS 29 13 223, suspended in an essentially nonremovable fashion from the outer flame tube wall, leaving a combined axial-radial play.
In a double-walled flame tube structure, the inner wall segments as well as the end segments of the air supply bushings, which are located primarily in the inner wall segment area, are exposed to a comparatively high temperature or temperature change stress by the combustion process, with the associated danger of burning away or corrosion by hot gases.
Since removal of one or more damaged air supply bushings is practically impossible for the mounting reasons referred to above, to the extent that it is even possible, it necessitates replacement of the flame tube wall parts affected and in extreme cases, replacement of the entire combustion chamber.
Usually, local repair of a damaged air supply bushing is impossible for safety reasons, not to mention the associated costs and time involved.
The shortcomings mentioned above also apply when, for example, the air supply bushings are intact but the flame tube structures are damaged, in which case one would be obliged to replace the damaged flame tube structures or the entire flame tube without putting back the intact bushings.
Assembly and disassembly difficulties occur with bushings that are permanently installed in the double-walled structure, especially when, as is increasingly the case in recent annular combustion chambers in gas turbine engines, the inner flame tube parts which are exposed to the hot or combustion gas stream are made of segments which extend lengthwise of the chamber and are staggered in the manner of shingles or scales. This is especially true when the segments or strip elements, because of their intrinsic assembly or for thermal stress reasons, are supposed to be pushed in the axial direction into the flame tube parts that are designed as outer or inner supporting elements, or are supposed to be pulled out of the latter, or suspended from them.
An object of the invention is to provide an air supply bushing which, relative to the predetermined flame tube double-walled structure, is readily interchangeable or extremely simply installed or demountable.
This stated object is achieved according to the invention by providing resilient retention means for detachably resiliently retaining the air supply bushings at one of the flame tube segments. With this arrangement the air supply bushing in question can be inserted very simply by hand, without special fitting measures, into the corresponding openings in the outer and inner flame tube segments of a double-walled flame tube structure and can likewise be pulled out easily again from the openings. In especially advantageous embodiments, the resilient annular spring element is used as the retention means.
In especially preferred embodiments, the air supply bushing is provided with a groove which accomodates compression of the locking ring to permit manual insertion of the bushing to a position where the ring resiliently and automatically snap-fittingly engages at the flame tube wall segment.
In certain preferred embodiments, access openings are provided in the flame tube segments to accommodate manual engagement of the locking ring to compress same for disassembly.
Further objects, features, and advantages of the present invention will become more apparent from the following description when taken with the accompanying drawings which show, for purposes of illustration only, several embodiments in accordance with the present invention.